Can't assign a shortcut to "Randomize"
So basically what you are facing is a shortage of appropriate shortcut options . You want to assign a shortcut which has R in it but you know that r is for rotating in all the modes , so you could've tried ctrl R but thats loop cut , alt R is clear rotation and shift r is repeat last action , so the final option is that you can go and add some other key like combinations of O for the shortcut because we are running out of shortcuts